Treating Recurrent Brain Metastases Using GammaTile Brachytherapy: A Case Report and Dosimetric Modeling Method

One of the treatment options for recurrent brain metastases is surgical resection combined with intracranial brachytherapy. GammaTile® (GT) (GT Medical Technologies, Tempe, Arizona) is a tile-shaped permanent brachytherapy device with cesium 131 (¹³¹Cs) seeds embedded within a collagen carrier. We report a case of treating a patient with recurrent brain metastases with GT and demonstrate a dosimetric modeling method.

Focal Prostate Stereotactic Body Radiation Therapy With Correlative Pathological and Radiographic-Based Treatment Planning

Introduction

Advances in multiparametric MRI (mpMRI) combining anatomic and functional imaging can accurately identify foci of adenocarcinoma within the prostate, offering the possibility of partial gland therapy. We performed tandem prospective pilot trials to investigate the feasibility of focal prostate SBRT (f-SBRT) based on correlating diagnostic mpMRI and biopsies with confirmatory pathology in treatment planning.

Materials and Methods

Patients with pathologic focal Gleason 6–7 disease and a corresponding PIRADS 4–5 lesion on mpMRI underwent targeted and comprehensive biopsies using MRI/ultrasound fusion under electromagnetic sensor navigation. After rigorous analysis for imaging biopsy concordance, five of 18 patients were eligible to proceed to f-SBRT. Chi-squared test was used for differences from expected outcomes, and concordance was estimated with binomial distribution theory and Wilson’s method.

Results

Six patients had Gleason 6 and 12 had Gleason 3 + 4 disease (mean PSA: 5.8 ng/ml, range: 2.2–8.4). Absolute concordance was 43.8% (95% CI: 0.20, 0.64). Patterns of discordance included additional sites of ipsilateral disease, bilateral disease, and negative target. Five were upstaged to a new NCCN risk category necessitating treatment escalation. The five patients with concordant pathology completed three-fraction f-SBRT with sparing of the surrounding normal structures (including contralateral neurovascular bundle), with no reported grade 2+ toxicities and favorable PSA responses (mean: 41% decrease).

Conclusions

On our pilot trials of f-SBRT planning using rigorous imaging and pathology concordance, image-guided confirmatory biopsies frequently revealed additional disease, suggesting the need for caution in partial-gland therapy. For truly focal disease, f-SBRT provided excellent dosimetry, minimal toxicity, and encouraging biochemical response. Clinical Trial Registration: www.clinicaltrials.gov, NCT02681614; NCT02163317.

Permanent Interstitial Cesium-131 Brachytherapy in Treating High-Risk Recurrent Head and Neck Cancer: A Prospective Pilot Study

Purpose/Objectives

To establish the feasibility and safety of intraoperative placement of cesium-131 (Cs-131) seeds for re-irradiation in recurrent head and neck cancer (HNC).

Methods

Patients with resectable recurrent HNC who were deemed to have a high risk of second recurrence were eligible. Immediately after tumor extirpation, seeds were implanted in the surgical bed based on the preoperative treatment plan with intraoperative adjustment. The surgical bed and the seeds were covered with a regional flap or microvascular free flap. A CT of the neck was obtained on postoperative day 1 for evaluation of the postoperative dose distribution. Patients were followed 1 and 3 months after surgery, then every 3 months in the first 2 years.

Results

From November 2016 to September 2018, 15 patients were recruited and 12 patients received treatment per protocol. For the patients who had implants, the sites of initial recurrence included 10 neck alone, 1 neck and larynx, and 1 neck/peristomal. The median follow-up was 21.4 months. After surgery, patients remained hospitalized for a median of 6 days. There were no high-grade toxicities except two patients with wound complications requiring wound care. Eight patients had recurrences, three locoregional alone, three distant alone, and two with both locoregional and distant recurrences. Only one patient had an in-field failure. Five patients died, with 1- and 2-year overall survival of 75 and 58%.

Conclusions

Cs-131 implant after surgical resection in recurrent HNC is feasible and safe. There were no unexpected severe toxicities. Most failures were out-of-field or distant.

Clinical Trial Registration

ClinicalTrials.gov, identifier NCT02794675.

Tumor localization accuracy for high-precision radiotherapy during active breath-hold

BACKGROUND

Conventionally fractionated and stereotactic body radiation therapy (SBRT) for thoracoabdominal tumors may utilize breath-hold techniques. However, there are concerns that differential amounts of inspired airflow may result in unplanned tumor dislocation and underdosing. Thus, we investigated tumor localization accuracy associated with lung volume variations during breath-hold treatment via an automated-gating interface.

METHODS

Twelve patients received breath-hold treatment with the active breathing coordinator (ABC) through an automated-gating interface. All breath-hold volumes were recorded at CT simulation, setup imaging, and during treatment, and analyzed as a function of airflow rate into the ABC. The variation of breath-hold volumes was calculated for each fraction over entire course. Intrafraction target motion related to the breathing variation was investigated based on daily imaging acquired before the breath-hold treatment. Correlation between target location and breath-hold variation was statistically analyzed.

RESULTS

The air volume held by the ABC increased as the airflow rate increased on inhalation and decreased on exhalation. The mean range of airflow rate was 0.77 L/s and 0.29 L/s in the conventionally fractionated and SBRT patients, respectively. The maximum air volume difference with respect to the reference volume at the CT simulation was 1.0 L for conventional fractionation and 0.16 L for SBRT. The target dislocation caused by 0.25 L of air volume difference was 6 mm for SBRT. Three patients showed significant correlation between the target location and breath-hold variations.

CONCLUSIONS

This investigation shows that because variations in the breath-hold volume may cause target dislocation, patient-specific breath-hold setting is required to improve tumor localization accuracy.

Comparison of multiparametric MRI-based and transrectal ultrasound-based preplans with intraoperative ultrasound-based planning for low dose rate interstitial prostate seed implantation

PURPOSE

Transrectal ultrasound images are routinely acquired for low dose rate (LDR) prostate brachytherapy dosimetric preplanning (pTRUS), although diagnostic multiparametric magnetic resonance imaging (mpMRI) may serve this purpose as well. We compared the predictive abilities of TRUS vs MRI relative to intraoperative TRUS (iTRUS) to assess the role of mpMRI in brachytherapy preplanning.

MATERIALS AND METHODS

Retrospective analysis was performed on 32 patients who underwent iTRUS-guided prostate LDR brachytherapy as either mono- or combination therapy. 56.3% had pTRUS-only volume studies and 43.7% had both 3T-mpMRI and pTRUS preplanning. MRI was used for preplanning and its image fusion with iTRUS was also used for intraoperative guidance of seed placement. Differences in gland volume, seed number, and activity and procedure time were examined, as well as the identification of lesions suspicious for tumor foci. Pearson correlation coefficient and Fisher's Z test were used to estimate associations between continuous measures.

RESULTS

There was good correlation of planning volumes between iTRUS and either pTRUS or MRI (r = 0.89, r = 0.77), not impacted by the addition of hormonal therapy (P = 0.65, P = 0.33). Both consistently predicted intraoperative seed number (r = 0.87, r = 0.86). MRI/TRUS fusion did not significantly increase surgical or anesthesia time (P = 0.10, P = 0.46). mpMRI revealed suspicious focal lesions in 11 of 14 cases not visible on pTRUS, that when correlated with histopathology, were incorporated into the plan.

CONCLUSIONS

Relative to pTRUS, MRI yielded reliable preplanning measures, supporting the role of MRI-only LDR treatment planning. mpMRI carries numerous diagnostic, staging and preplanning advantages that facilitate better patient selection and delivery of novel dose escalation and targeted therapy, with no additional surgical or anesthesia time. Prospective studies assessing its impact on treatment planning and delivery can serve to establish mpMRI as the standard of care in LDR prostate brachytherapy planning.

Assessment of beam-matched linacs quality/accuracy for interchanging SBRT or SRT patient using VMAT without replanning

PURPOSE

Dosimetric accuracy is critical when switching a patient treated with stereotactic body radiation therapy (SBRT) or stereotactic fractionated radiotherapy (SRT) among beam-matched linacs. In this study, the dose delivery accuracy of volumetric modulated arc therapy (VMAT) plans for SBRT/SRT patients were evaluated on three beam-matched linacs.

METHOD

Beam data measurements such as percentage depth dose (PDD₁₀ ), beam profiles, output factors, and multi-leaf collimator (MLC) leaf transmission factor for 6 MV photon beam were performed on three beam-matched linacs. The Edge™ diode detector was used for measurements of beams of field size less than 5 × 5 cm² . Ten lung and 15 brain plans were generated using VMAT with the same beam model. Modulation complexity score of the VMAT plan (MCSv) was used as a plan complexity indicator. Doses were measured using ArcCHECK™ and GafChromic™ EBT3 films. The measurements were compared with calculated doses through absolute dose gamma comparison using 3%/2 mm and 2%/2 mm criteria. Correlation between difference in passing rates among beam-matched linacs and MCSv was evaluated using the Pearson coefficient. Point doses were measured with the A1SL micro ion chamber.

RESULTS

Difference in beam outputs, beam profiles, and MLC leaf transmission factors of beam-matched linacs were all within ±1%, except the difference in output factor for 1 × 1 cm² field between linac 1 and 3 (1.3%). For all 25 cases, passing rates of measured doses on three linacs were all higher than 90% when using 2%/2 mm gamma criteria. The average difference in point dose measurements among three beam-matched linacs was 0.1 ± 0.2% (P > 0.05, one-way ANOVA).

CONCLUSION

Minimal differences in beam parameters, point doses, and passing rates among three linacs proved the viability of swapping SBRT/SRT using VMAT among beam-matched linacs. The effect of plan complexity on passing rate difference among beam-matched linacs is not statistically significant.

3T multiparametric MRI-guided high-dose-rate combined intracavitary and interstitial adaptive brachytherapy for the treatment of cervical cancer with a novel split-ring applicator

PURPOSE

To evaluate the role of 3T-MRI-guided adaptive high-dose-rate (HDR) combined intracavitary and interstitial brachytherapy for cervical cancer using a novel intracavitary split-ring (ICSR) applicator adapter.

METHODS AND MATERIALS

We retrospectively reviewed all HDR brachytherapy cases from 2013 to 2015 using an ICSR applicator. Initial optimization was performed using 3T multiparametric MRI (mpMRI) series with an applicator in place. The mpMRI series were discretionarily acquired before subsequent fractions for possible target adaptation. When necessary, interstitial needles (ISNs) were inserted through a novel ICSR adapter or freehand. Dosimetric parameters, clinical outcomes, and toxicities were compared between groups.

RESULTS

Seventeen patients were included, with a mean followup of 32 months. An mpMRI series preceded each initial fraction and 52.9% of patients underwent ≥1 additional pretreatment mpMRI. Among these subsequent fractions, the high-risk clinical target volume was reduced in 80% vs. 41% without pretreatment mpMRI. Five patients had ISN placement (seven insertions) to improve extracervical target coverage. Mean D₉₀ (Gy) per fraction to the high-risk clinical target volume and intermediate-risk clinical target volume with and without an ISN were 7.51 ± 1.07 vs. 6.14 ± 0.52 (p = 0.028) and 6.35 ± 0.75 vs. 5.21 ± 0.49 (p = 0.007), respectively. Mean fractional D_2cc (Gy) for organs at risk was comparable. No Grades 3-4 toxicity was reported. Disease-free survival and local control for the ICSR-ISN and ICSR-alone groups were 29.8 months/80.0% and 31.2 months/83.3%, respectively.

CONCLUSIONS

The mpMRI acquisition with ICSR applicator in place immediately before HDR brachytherapy for cervical cancer guided successful adaptive treatment optimization and delivery. Our initial experience with a novel interstitial adapter for the split-ring applicator demonstrated excellent target coverage without compromising organs at risk, resulting in good local control and disease-free survival.

Closed loop control of a robot assisted smart flexible needle for percutaneous intervention

This paper presents the experimental evaluation of a coordinated control system for a robot and robot-driven shape memory alloy (SMA) actuated smart flexible needle capable of following a curved path for percutaneous intervention. The robot driving the needle is considered the outer loop and the non-linear SMA actuated flexible needle system comprises the inner loop. The two feedback control loops are coordinated in such a way that the robot drives the needle while monitoring the needle's actual deflection against a preplanned ideal trajectory, so that the needle tip reaches the target location within an acceptable accuracy. In air and in water experimental results are presented to validate the ability of the proposed coordinated controller to track the overall desired trajectory which includes the combined trajectory of the robot driver and the needle.

Effect of Race and Insurance on the Outcome of Stage I Non-small Cell Lung Cancer

BACKGROUND

Lung cancer is the leading cause of death in the United States, with reported inferior survival among African-Americans.

PATIENTS AND METHODS

Kaplan-Meier and Cox regression methods were used to compare survival outcomes of 569 patients diagnosed with stage I non-small cell lung cancer from 2001-2010.

RESULTS

African-Americans and Whites differed significantly by age, sex, and insurance type. The median follow-up was 2.3 years. The 2-, 5- and 8-year overall survival was 72%, 47%, and 38%, respectively. Age, stage, insurance type, and surgery were significant predictors of overall survival which remained significant after adjusting for other variables, including race, gender, histology, smoking history, treatment era, chemotherapy or radiotherapy which were not.

CONCLUSION

Insurance status but not race is an important predictor of survival in patients with stage I non-small cell lung cancer.

Comparison of Ray Tracing and Monte Carlo Calculation Algorithms for Thoracic Spine Lesions Treated With CyberKnife-Based Stereotactic Body Radiation Therapy

Stereotactic body radiation therapy (SBRT) is an emerging technology for the treatment of spinal metastases, although the dosimetric impact of the calculation method on spinal dose distribution is unknown. This study attempts to determine whether CyberKnife (CK)-based SBRT using a Ray Tracing (RyTc) algorithm is comparable dosimetrically to that of Monte Carlo (MC) for thoracic spinal lesions. Our institutional CK-based SBRT database for thoracic spinal lesions was queried and a cohort was generated. Patients were planned using RyTc and MC algorithms using the same beam angles and monitor units. Dose-volume histograms of the planning target volume (PTV), spinal cord, esophagus, and skin were generated, and dosimetric parameters were compared. There were 37 patients in the cohort. The average percentage volume of PTV covered by the prescribed dose with RyTc and MC algorithms was 91.1% and 80.4%, respectively (P < .001). The difference in average maximum spinal cord dose between RyTc and MC plans was significant (1126 vs 1084 cGy, P = .004), with the MC dose ranging from 18.7% below to 13.8% above the corresponding RyTc dose. A small reduction in maximum skin dose was also noted (P = .017), although no difference was seen in maximum esophageal dose (P = .15). Only PTVs smaller than 27 cm(3) were found to correlate with large (>10%) changes in dose to 90% of the volume (P = .014), while no correlates with the average percentage volume of PTV covered by the prescribed dose were demonstrated. For thoracic spinal CK-based SBRT, RyTc computation may overestimate the MC calculated average percentage volume of PTV covered by the prescribed dose and have unpredictable effects on doses to organs at risk, particularly the spinal cord. In this setting, use of RyTc optimization should be limited and always verified with MC.

Development of a coordinated controller for robot-assisted shape memory alloy actuated needle for prostate brachytherapy

This paper deals with the development of a coordinated control system for a robot and robot-driven shape memory alloy (SMA) actuated needle to follow a curvilinear path for percutaneous intervention. The robot driving the needle is considered as the outer loop and the non-linear SMA actuated flexible needle system forms the inner loop. The two feedback control loops are coordinated in such a way that the robot drives the needle considering the needle's actual deflection so that the needle tip reaches the target location with an acceptable accuracy. Simulation results are presented to verify the efficacy of the controller for tracking the overall desired trajectory which includes the combined trajectory of the robot and the needle.

Race, insurance type, and stage of presentation among lung cancer patients

The purpose of this study was to determine whether African-American lung cancer patients are diagnosed at a later stage than white patients, regardless of insurance type. The relationship between race and stage at diagnosis by insurance type was assessed using a Poisson regression model, with relative risk as the measure of association. The setting of the study was a large tertiary care cancer center located in the southeastern United States. Patients who were diagnosed with lung cancer between 2001 and 2010 were included in the study. A total of 717 (31%) African-American and 1,634 (69%) white lung cancer patients were treated at our facility during the study period. Adjusting for age, sex, and smoking-related histology, African-American patients were diagnosed at a statistically significant later stage (III/IV versus I/II) than whites for all insurance types, with the exception of Medicaid. Our results suggest that equivalent insurance coverage may not ensure equal presentation of stage between African-American and white lung cancer patients. Future research is needed to determine whether other factors such as treatment delays, suboptimal preventive care, inappropriate specialist referral, community segregation, and a lack of patient trust in health care providers may explain the continuing racial disparities observed in the current study.

Chest wall and rib irradiation and toxicities of early-stage lung cancer patients treated with CyberKnife stereotactic body radiotherapy

ABSTRACT 

Aim: The aim of the study is to evaluate the chest wall and rib toxicities in primary lung cancer patients treated with CyberKnife-based stereotactic body radiotherapy. Materials & methods: In this study, data were collected from the 118 patients, of which 25 patients who had longer follow-up (mean: 21.9 months) were considered. Studied parameters were maximum point dose, doses to 1–100 cm3 of chest wall and 1–10 cm3 of ribs. Results: Three patients developed chest wall pain (grade I). 25 studied patients, on average, received 27.7 Gy to 30 cm3 of chest wall and 50.4 Gy to 1 cm3 of rib. Nine patients had more than 30 Gy dose to 30 cm3 of chest wall. No rib bone fracture was found. Conclusion: No correlations of chest wall pain and volume of irradiation were found.

Important prognostic factors for lung cancer in tobacco predominant Eastern North Carolina: study based on a single cancer registry

BACKGROUND

It is known that lung cancer incidence and mortality rate are higher in African Americans (AA) than whites. In Eastern North Carolina, there is a higher percentage of AA population than the national average (30.2% vs. 12.4%) and a higher incidence of lung cancer in this region. We investigated demography and survival of lung cancer patients diagnosed and treated in a single institution.

METHODS

The study includes 2351 patients diagnosed with lung cancer between 2001 and 2010 at East Carolina University. AA and whites were compared by age, sex, race, stage, histology, smoking history and insurance information using chi-square analyses. Patient survival was modeled using Cox proportional hazards regression (SAS version 9.2).

RESULTS

The distribution of lung cancer was 70% in whites and 30% in AA. The proportion of AA and whites differed significantly for age, sex, histology, stage, and insurance. Patients aged > 70 (p < 0.0001) and 51-70 (p = 0.0064) died sooner than those ≤ 50 years old. Compared with squamous cell, SCLC had inferior survival (HR = 2.0, 95% CI = 1.7-2.3). Privately insured patients survived longer than those with medicare (p < 0.0001), medicaid (p = 0.0009), or no insurance (p < 0.0001). The survival disadvantage for medicaid (p = 0.0076) and no insurance (p = 0.0033) persisted on multivariable analysis. Race was not a significant predictor of survival on multivariable analysis (p = 0.66).

CONCLUSION

This is one of the largest lung cancer patient populations from a single institution showing demographic differences between the two races with similar survival outcome. Age, histology and type of insurance were strong predictors of survival outcome. Older age, small cell histology and medicaid and no insurance had significantly shorter overall survival.

SU-E-T-412: Can Cyberknife SBRT Be an Alternative to Brachytherapy for Cervical Cancer Treatment?

PURPOSE

To investigate the effectiveness of stereotactic body radiation therapy (SBRT) with Cyberknife for treatment of squamous cell carcinoma (SCCa) of cervix that are commonly treated with brachytherapy.

METHODS

SCCa of cervix is routinely treated with external beam radiation therapy (EBRT) followed by brachytherapy. Common practice is to use high-dose- rate (HDR) brachytherapy, mainly with Ir-192; however, low-dose-rate (LDR) brachytherapy with Cs-137 is also used. Three of our patients with cervical SCCa who were chosen to have LDR brachytherapy (Cs-137 with tandem and ovoids) could not tolerate the prolonged treatment or applicator placement. All these patients previously received 45Gy (1.8Gy/fratction) from EBRT and well tolerated. Planned LDR treatment dose and time were for patient-1: 42.63Gy in 73.5hr, patient-2: 42.34Gy in 73hr, patient-3: 41.76Gy in 72hr. Delivered LDR dose and time were: 3.75Gy in 6.5hr, OGy in Ohr, and 17.3Gy in 19.8hr, for patient-1, -2 and -3, respectively. Two of the three patients tolerated LDR treatment partially; the second patient could not tolerate the applicator, which required immediate removal after placement. Treatments were completed with Cyberknife SBRT (CK-SBRT)doses of 25Gy, 15Gy and 25Gy for patient-1, -2 and -3, respectively; all had 5Gy/fraction and 3fractions/week. Prescriptions were at 80% isododelines; CTV coverages were 96.6%, 99.9% and 100% for patient-1, -2 and -3, respectively.

RESULTS

Till their last follow-up in February 2012, all three patients were doing fine clinically without any evidence of disease; none of these patients had any complications that could be related to CK-SBRT.

CONCLUSIONS

Appears that CK-SBRT can be a viable treatment alternative to brachytherapy. CK-SBRT may also be more appealing to patients and physicians for a variety of reasons such as out-patient procedure, shorter treatment time, no need for operating room, and no need for applicator insertion and tolerance. However, extensive clinical study is warranted in this regard.

SU-E-T-422: Lung SBRT Using Cyberknife: Technique and Treatment Outcome

PURPOSE

At East Carolina University, we have been treating primary and secondary lung cancers with Cyberknife stereotactic body radiotherapy (CK- SBRT) since February 2009. Till October 2011, we have treated a total of 79 patients (83 sites). In this study, we present our experience in CK-SBRT and clinical outcome of the treated patients.

METHODS

Of the 79 patients, 43 were female; age of the whole patient population ranged 33.2-89.7yrs (median=73.2yrs). Patients treated for primary lung cancer (n=57) had severe chronic obstructive pulmonary disease (COPD) and were not surgical candidates. Cyberknife robotic system with tracking techniques (Synchrony=52, XsiteLung=22, XsightSpine=5) were used. Majority of the patient (n=52) had multiple gold fiducials placed (1-6 placed; 1-4 tracked per patient) either percutaneously or bronchoscopically. CT images were used for dosimetric planning, by medical physicists, using Cyberknife MultiPlan software. Prescription doses were 25Gy-55Gy in 3-5 fractions (mean=48.2Gy, median=50Gy); doses were prescribed mainly to 80% isodoseline (range=75-96%, mean=81.4%). PTV margin varied from 0-7mm (mean±SD=3.2±1.4mm), based on the tumor locations; breathing patterns and cancer type. Dosimetric coverage of GTV and PTV were (mean±SD): 97.8±5% and 94.7±6.9%, respectively. The treatment response was assessed using either a CT or a PET scan or both.

RESULTS

The median follow up was 13.1months (range 0.3-31.9 months). Overall response rate was 98.8% (CR=73.5%). Local failure free survival at one year was 84% for primary (n=57), 76% for recurrent (n=16) lung cancer and 100% for metastatic (n=10) tumors. The toxicity rate was low with one patient reported to have chest wall pain and one patient developed grade 3-4 radiation pneumonitis.

CONCLUSIONS

In most of the cases tight PTV margins were used. Since the prescriptions were at 80% isodeose line with more than 94% PTV coverage, the treatment outcome appeared reasonable. Further study relating PTV margin, dosimetric coverage, and treatment outcome is in progress.